Characterization of keratins from rat cervical epithelial cells in vivo and in vitro

The keratins expressed in cultured rat cervical epithelial cells were analyzed by using two-dimensional gel electrophoresis and monoclonal antikeratin antibodies and were compared with those expressed in the rat cervix in vivo in the presence and absence of estrogen stimulation. The cervical epithelium in vivo responds to estrogen stimulation with alterations in keratin composition. In response to estrogen, the epithelium undergoes proliferation and stratification and begins expressing increased amounts of two basic Mr 57,000 and 58,000 keratins and two acidic Mr 51,000 and 52,000 keratins. Cultured rat cervical epithelial cells were found to express only small amounts of the basic Mr 57,000 and 58,000 keratins and the two acidic Mr 51,000 and 52,000 keratins characteristic of the estrogen-stimulated cervix. In addition to the keratins found in the cervical epithelium in vivo, rat cervical epithelial cells in vitro begin expressing two Mr 55,000 and 56,000 keratins of the basic keratin family (type II) and an acidic component with a molecular weight of 40,000. Although these components are not detected in the rat cervix in vivo, they migrate similarly on two-dimensional electrophoretic gels to proteins expressed by the rat endometrial epithelium in vivo. These findings indicate that alterations in keratin expression could serve as markers for studying the effects of steroid hormones on the differentiation of rat cervical epithelial cells in vitro and during the development of squamous metaplasia.